Unless you know something about suspension, stick with one of the kits. You could just get the Heidt crossmember and salvage the rest of the parts. Its only about $400.00. If you get things like the anti-dive wrong, it will never feel good.
But you asked how hard it would be. If you can weld, it wouldn't be hard. You would likely ahve to build it several times to get it right. You would have to study some suspension books and do some math. Not hard, but hard to do right the first time.
But you asked how hard it would be. If you can weld, it wouldn't be hard. You would likely ahve to build it several times to get it right. You would have to study some suspension books and do some math. Not hard, but hard to do right the first time.